Fire alarm system



Oct. 16, 1934. o. l. H. EKMAN 1,977,121

FIRE ALARM SYSTEM 1 Filed Sept. 1. 192'! s Sheets-Sheet 1 Ta I T PIPOTECTED FIFE CENT/F591.

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Oct. 16, 1934. o. l. H. EKMAN 1,977,121

FIRE ALARM SYSTEM Filed Sept. 1, 1927 3 Sheets-Sheet 2 Alz ay FT'TOIP/YEXS 0d. 16, 1934. o. I. H. EKMAN 1,977,121

FIRE ALARM SYSTEM Filed Sept. 1, 1927 3 Shedts-Sheet 5 awe-N703: O: I. Kma t 5y /MWMML Patented Oct. 16, 1934 UNITED STATES PATENT orrics f FIRE ALARM SYSTEM Application September 1, 1927, Serial No. 216,978 In Sweden September 11, 1926 4 Claims.

The invention relates to such fire alarm sys terns which are provided with signal means for automatically signalling the outbreak of fire as well as faults, and in which said signal means I are arranged to be operated over control circuits forming conductor loops extending through the localities to be protected and consisting of two line branches connected in series over a source of current and a control relay and carried at each locality protected over two switches operative in the event of fire and connected each into a line branch. The invention is based on the fact that such interruptions in the control circuit which may arise from faults in the electrical conductor II system will occur very seldom in both line branches at a time, whereas the outbreak of a fire will always cause both line branches to be broken. This fact is utilized according to the present invention for the control of the fire and fault signals. To this end the fire and fault signal means are arranged according to the invention under the control of said control relay and one or more fault relays, the latter being arranged to operate under the control of the switches in the conductor loop so as to connect up a fault signal upon an interruption in one line branch only and a fire alarm signal upon an interruption in both line branches.

The arrangement is preferably such that the 3 conductor loop and the control relay included therein are normally current-carrying. In order to reduce as far as possible the current con-'- sumption, said fault relays are then normally currentless and arranged to be brought in oper- 5 ation through the medium of the control relay which on account of its arrangement in the conductor loop will be de-energized both in case of fire and in case of fault. Preferably the circuits of the fault relays are arranged under the con- 40 trol of the control relay in such a manner as to be closed over the conductor loop upon the control relay being de-energized as a consequence of a fault in the loop. v V

The invention will be more closely described with reference to the accompanying drawings, in which Figure 1 shows a circuit diagram of a fire alarm system. According to the invention, Figures 2 and 3 show circuit diagrams of another embodiment of the invention.

In Figure 1, A1 designates a loop connected to the central apparatus.

The one branch L1 of each loop extends from the one terminal (for instance the plus terminal) of a battery B1, and is extended over a series of normally closed thermostat contacts a and connected at its opposite end with the other branch L2 of the loop over a control relay R. The branch L2 is extended back, running parallel. with the branch L1 over a series of thermostat contacts I). Preferably, the contacts a and b are united in pairs to units of apparatus T and adapted to be opened simultaneously in case of fire. l"he branch L2 of the loop is not connected directly to the other terminal (the minus terminal) of the battery, but is first extended over a normally 651 closed contact 761 in the set of contacts of the relay R and, preferably, also over a resistance FM. Otherwise, the arrangement is believed to be best understood from the following explanation'of its mode of operation. 70,

Normally, the relay R is kept energized through the current over the closed loop, the contact In being then closed, while the other contacts are open.

If the loop A1 is actuated by a fire, so that the 75, contacts a, b of one or more thermostats are opened, the lines L1 and L2 are interrupted and the relay R becomes currentless so that it will release its armature. The contact In is broken, but in the present instance this has no consequences. The other contacts of the relay are closed. The relay R is short-circuited at the contact 762, but this also has no consequences in the present instance. At ks, a relay TR operating with time retardation is connected into a circuit extending from the plus terminal of the battery B1 over the wire 0, the relay TR and the contact kg to the minus terminal of the battery B1. When on the lapse of a certain time the armature of relay TR is attracted, it short-circuits the normally ener- 'gized fire box relay BR at the working contact tn of the relay TR as well as over a back contact in at the unactuated fault relay FR, said relay BR then releasing its armature and closing its back contacts. At the contact bTl, the minus side of the battery B1 is connected to the one bus bar MSK of the alarm bells, whereas the corresponding other bus bar PSK is connected over contacts in at the relay TR and the wire 0 to the plus side of the battery B1. Alarm bells AK and a fire alarm lamp AL connected between the bus bars are actuated and indicate the outbreak of a fire. The localization of the fire to the loop A1 is indicated by the signal lamp SL individual to A1,

said lamp being connected up to the battery B1 over the contacts R4, 763 and a wire 6 at the relay B when the latter becomes currentless.

,A. main fire box relay HBS is normally connected in series with the fire box relay BR and, consequently, will not obtain current enough to be brought into function. On the attraction of the relay TR, however, the main fire box relay I-IBS was connected over tn and in to the battery past BR. Consequently, this relay will now be operated and signals the main fire box.

If an interruption occurs in the one or the other branch of the loop, for instance in L2, the current will be interrupted through the control relay R, which releases its armature and makes the same breaks and closes in its set of contacts as above indicated. The battery is then switched over, so that the two branches of the loop are connected in parallel between the terminals of the battery, in that L2 is shifted from the minus terminal of the battery to the plus terminal thereof over k6. At the opposite end, the two branches of the loop are connected over the contacts In and ks, the wide (1 and the fault relay FR to the minus terminal of the battery B1. Thus the fault relay FR is energized by current over the noninterupted line branch L1 and then breaks its back contact fr1 and closes its working contact frz.

This takes place, before the slow-acting relay TR, which is connected into circuit in the manher before described, has time to enter into function. Thus short-circuiting of the relay BR is prevented at in, said relay, therefore, remaining operative also upon attraction of TR. Consequently, the relay IIBS remains inoperative, and thus no fire alarm will be caused either in the alarm apparatus AK or in the main fire box.

At the contact in. of the relay FR, the fault signal lamp FL and the fault signal bell FK are connected to the battery. Likewise, the individual signal lamp SL is connected into circuit as before, thus indicating that the fault is to be found in the loop A1.

A break in L1 acts in a manner analogous to that above described.

If a one-sided earth connection takes place, the relay JR. connected between earth and the middle point of the battery B1 will be currentcarrying over the one half part of the battery and the branch conductor subjected to the earth connection, the said relay then closing its contacts in and in. Hereby the earth connection signal lamp JL is connected into circuit and indicates that the fault consists in an earth connection. At the same time FL and FK are connected into circuit.

If a short-circuit takes place, the relay R is disconnected as before. The current from the battery B1 flows through the short-circuit, over the contact k1, and thus the battery will be shortcircuited, until the relay R is disconnected, which, practically, takes place instantaneously. However, in order to prevent the contact 101 from burning cut, the resistance FM is connected between the battery and the contact 701 after the other tappings from the terminal in question of the battery. In this case the fault relay FR is connected into a circuit extending from the plus terminal of the battery over the branch L1 and the contact its and the relay FR to the minus terinal of the battery. Thus the action will be the same as on a simple break.

In the case of a dcuble-sided earth connection the function will be the same as in the event of a short-circuit, besides which the relay JR is connected into circuit as in the case of a simple earth connection, and connects the earth connection signal lamp JL into circuit, if the earth connections are not of the same value.

In the event of a double-sided interruption which, practically, only takes place at the outbreak of a fire, an increase of the tension will take place at the moment of interruption by reason of self-induction, so that sparking over may be feared at some weak point of the insulation of the conductor. A fault of this kind or some other fault occurring at this moment must not, however, prevent the fire alarm from being conveyed, whether the fault occurs on the one or the other side of the thermostat actuated. It is assumed that the thermostat designated by Ta has been actuated and has opened the two branches L1 and L2, and that a puncture, that is to say a short-circuit, takes place on the interruption between the relay R. and the thermostat as at I. In this instance, the puncture only involves short-circuiting of the relay R over itself and thus aids toward making the relay currentless. In this case, the fault will thus increase the safety for the relay R de-energizing.

If a puncture occurs between the branches of the loop at a point between'the thermostat and the battery, as at II, this will have no injurious consequences for the alarm signal, inasmuch as the lines are broken at the thermostat and energization of the fault relay FR. cannot, therefore, take place. Short-circuiting of the battery is in this case prevented automatically by the opening of the contact k1 of the relay R, as stated hereinbefore.

Figure 2 shows another embodiment in which there are provided two fault relays PR1 and FRz, one relay being provided for each branch of the loop. Said relays are normally disconnected and adapted to be connected up to the corresponding branches of the loop over back contacts k7, ks of the control relay R the latter being included in the loop circuit and arranged to operate in the same way as in Figure 1. When the relay R deenergizes in the event of a fire or on a fault occurring, a test circuit is formed as in Figure 1 for testing the condition of the loop said circuit including the two line branches L1, L2, connected at one end, to the opposite poles of the battery B1 through resistances M1 and M2 respectively and at the other end to the middle point of the battery over contacts R12, 7013 of the relay R. In case of a fire both said branch circuits are open. In case of a fault consisting of a breakage in one line branch the test circuit will be closed only over the other line branch and in case of a short circuit in the loop the test circuit will be closed through both line branches. Upon the deenergization of the relay R, the fault relays FR1, FRz will be associated with said test circuit over the contacts k7, 758 each fault relay being thereby connected up between a point m1 or 1112 respectively of the appertaining line branch and the opposite ends of the line branches at the point n connected to the middle point of the battery.

fault relays will be short-circuited by the appertaining line branches in case there is no interruption in the line branches, whereas in case one or the other or both line branches are interrupted the one or both fault relays will energize, in a circuit including the contact In or its respectively, the resistance M1 or M2 respectively and the corresponding half of the battery B. In the event of fire both relays FR1 and F132 are rendered operative the fire box relay BR being then shortcircuited over contacts g, it connected in series thus causing the main fire box relay HBS to operate as described in connection with Figure 1.

Fault signalling means may be provided similar to those shown in Figure 1.

Figure 3 shows another modification in which the control relay R is adapted upon de-energizing to form a test circuit extending from the positive pole of the battery through the two branches of the loop connected in parallel, the line branch L2 having been connected to the positive pole of the battery over the contact kn of the relay R, and further through the two halves of the winding of the relay R and a back contact In; on said relay through the relay AR to the negative pole of the battery. The relay AR which will energize in said circuit when there is no interruption in the line branches or when only one line branch is interrupted, whereas in case both line branches are interrupted as in case of fire, said relay AR will deenergize and shortcircuit the fire box relay BR over its contact 12 with the effect of causing the main fire box relay HES to operate. The relay AR is normally kept energized in a circuit extending from the positive pole of the battery over a resistance W1 and the contact km of the relay R through AR to the negative pole of the battery. Normally the line branch L2 is connected to the negative pole of the battery W2 adapted to prevent shortcircuiting of the battery when the said test circuit is formed.

The invention may also be applied to fire alarm plants having fire boxes adapted to be manually actuated in place of automatic thermostats, as well as to Water sprinkling plants with automatically active extinguishing means, the circuit breaking members being then arranged to be actuated by any member operative in such a plant in the event of a fire.

I claim: 7

1. In an alarm system, a source of current, a control relay, a closed protective circuit including a pair of adjacent line wires normally connected at one end to opposite terminals of said source of current and at the other end with one another through the Winding of said control relay, a circuit closer in each of said line wires adapted to be simultaneously actuated to open both of the line wires, contacts controlled by the de-energization of said control relay, one of said contacts controlling a circuit adapted to connect one end of both of said line wires to. one terminal of said battery, a second of said contacts controlling a circuit adapted to connect the other end of both of said line wires to the other battery terminal through the winding of a second relay, a trouble circuit controlled by the energization of said second relay and means including an alarm circuit controlled by the de-energization of both of said relays, whereby a trouble signal is given if one of said line wires is interrupted and an alarm is given if both of said line wires are interrupted.

2. An alarm system as claimed in claim 1, in which one line wire is normally connected to the corresponding terminal of the source of current over a front contact on the control relay and adapted to be connected to the opposite terminal of the source of current over a back contact of said relay.

3. In an alarm system a source of current, a control relay, a normally closed protective circuit including a pair of adjacent line wires normally connected at one end to opposite terminals of said source of current and at the other end with one another through the winding of said control relay, circuit closers in said line wires adapted to be actuated to open both of the line wires, two temporary circuits each including one of said line wires and back contacts of said control relay, a relay device included in said temporary circuits and differently responsive to simultaneous breaks in both line wires and to a break in one line wire alone, and alarm and trouble circuits, said relay device including means for controlling said alarm and trouble circuits whereby an alarm is given when both line wires are open at the same time and a trouble signal is given when either of the line wires is open alone.

4. An alarm system as claimed in claim 3, in which the temporary circuits include both line wires connected in parallel.

OLOF INGEMAR HARALD EKMAN. 

